The strong growth in demand for portable consumer electronics is driving the need for high-capacity storage devices. Non-volatile semiconductor memory devices, such as flash memory storage cards, are widely used to meet the ever-growing demands on digital information storage and exchange. Their portability, versatility and rugged design, along with their high reliability and large capacity, have made such memory devices ideal for use in a wide variety of electronic devices, including for example digital cameras, digital music players, video game consoles, PDAs and cellular telephones.
Recently, ultra high density memory devices have been proposed using a 3D stacked memory structure having strings of memory cells formed into layers. One such storage device is sometimes referred to as a Bit Cost Scalable (BiCS) architecture. In addition to the layered memory cells, 3D memory devices include a logic circuit for controlling read/write to the memory cells. The logic circuit, often fabricated using complementary metal-oxide-semiconductor (CMOS) technology, may typically be formed beneath stacked memory layers within a semiconductor wafer.
As the number of memory layers in 3D memory structures increases to meet ever growing memory demands, it is becoming harder to position the logic circuit beneath the 3D memory cell structure. Additionally, process parameters which are optimized for the memory array formation may not be optimized for the logic circuit formation. For example, it is known to anneal the 3D memory cell structure with heat. While advantageous for the memory cell structure, the heat can adversely affect the operation of the logic circuit.